Energy utilization of coal-coking wastes via coal slurry preparation: The characteristics of slurrying, combustion, and pollutant emission

Coal coking technology produces a large amount of refractory wastewater and sludge with complex components and low biodegradability. The coking wastes prepared as coal slurry, which is then used as liquid fuel, can diminish their polluting effects on the environment and transform themselves as resources. Slurrying, combustion, and pollutant emission characteristics of coking wastes coal slurry, including coking wastewater–coal slurry (CWCS) and coking sludge–coal slurry (CSCS), are the focus of this study. Results show that coking wastewater is good for the slurrying of the coal slurry. The maximum slurrying concentration of the CWCS was 62.16%, whereas that of the common coal water slurry (CWS) was 61.36%. By contrast, the coking sludge exhibited adverse effect on the slurrying of the CSCS due to the presence of abundant internal voids and hydrophilic functional groups. The coal slurry prepared from coking wastes showed slight influences on the ignition, burn out, and SO2 emission. Meanwhile, the emission peaks of NO and HCN increased. Specifically, NO increased from 45 ppm (CWS) to approximately 68 ppm (CWCS) and 90 ppm (CSCS), while HCN increased from 11 ppm (CWS) to approximately 22 ppm (CWCS) and 20 ppm (CSCS). Furthermore, the additional Cd, Cr, Ni, Pb, and Zn were volatilized, which resulted in the slightly lower content retained at the bottom ash. •Coking wastes were used to prepare coal slurry fuel.•The organic components of coking wastewater improved the slurrying ablility.•Coking sludge was ultrasonically dispersed to improve its slurrying ablility.•Coking wastes had negligible influences on the combustion of coal slurry.•More heavy metals were volatilized during the combustion of coking waste-coal slurry.